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report. The factors which seem to have no correlation to the air overpressures were pounds per delay and total pounds of explosives. There does seem to be a direct relationship between the high air overpressures and the number of holes, atmospheric conditions, and the blasting locations" (pg 10). Though the Vibra-Tech study suggested three factors that influenced air blast levels during the study conducted at the Trapper Mine, the US Bureau of Mines Report of Investigations 8485, "Structure Response and Damage Produced by Airblast from Surface Mining, 1980"; which was referenced in the Vibra-Tech study, lists several additional factors that can influence airblast levels, including "chazge weight, distance, delay intervals, face orientation, (and) explosive confinement" (pg 66). The Vibra-Tech study additionally referenced the ISEE Blasters' Handbook (17~' ed), which lists eleven factors that can affect blasting overpressures, including maximum chazge weight per delay, chazge burial depth, and topography (pgs 634-641). The Vibra-Tech study documented that air blast levels monitored during the study (July 10,2003 through October 14, 2003) all fell below the 133 dB regulatory maximum for the monitoring equipment used (2.0 Hz low-end sensitivity); however, the study documented that monitoring inadvertently did not occur at three intervals during the study (July 14-26 at the "Davis Residence" station, September 6-October 14 at the "NE Corner" station, and September 29-October 14 at the "Davis Residence" station). This lack of monitoring data prevents the Division from knowing whether the 133 dB limit was exceeded during these intervals. The high number of variables that can affect airblast levels at the Trapper Mine, as documented in the Vibra-Tech study and in the study's referenced materials, combined with the understanding that surface coal mine blasts at the Trapper mine will vary in design, location, and orientation, prevents the Division from concluding that every future blast at the Trapper Mine will be identical to those conducted during the Vibra-Tech study. This in turn prevents the Division from concluding that airblast levels from every future blast will be below the 133 dB limit. Further, some of the Trapper Mine pits have changed location, topography, and pit and face orientations slightly since the study was completed in October 2003, with some of the pits now situated closer to the monitored structures than during the Vibra-Tech study. This renders some of the conclusions from the Vibra-Tech study somewhat inapplicable to present and future blasting at the Trapper mine. The Division therefore believes that monitoring of airblast levels from every blast is necessary to verify compliance with the state regulatory limits set forth in Rule 4.08.4(6)(a). Please replace the sentence in Section 3.4.3 (page 3-31) that states "Trapper commits to conduct periodic air blast monitoring" with a new sentence that states "Trapper commits to conduct air blast monitoring of every blast". It should be noted that this requirement is consistent with the Division's airblast monitoring Trapper Mine Page 7 6/29/2005 Midterm Review